1. Field of the Invention
This invention relates to circuit breakers for protecting electric power circuits and, more particularly, to such circuit breakers including a set of main contacts and a set of secondary contacts in series with the main contacts. The invention also relates to an electrical distribution panel including one or more circuit breakers having a set of main contacts and a set of secondary contacts in series with the main contacts and, in particular, to such an electrical distribution panel which monitors such circuit breakers.
2. Background Information
Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high-level short circuit condition.
Circuit breakers used in residential and light commercial applications are commonly referred to as miniature circuit breakers because of their limited size. Such circuit breakers typically have a pair of separable contacts opened and closed by a spring biased operating mechanism. A thermal-magnetic trip device actuates the operating mechanism to open the separable contacts in response to persistent overcurrent conditions and to short circuits. Usually, circuit breakers of this type for multiple circuits within the residence or commercial structure are mounted together within a load center or panelboard, which may be located in a basement or other remote location. In some applications, it has been found convenient to use the circuit breakers for other purposes than just protection, for instance, for load shedding. It is desirable to be able to perform this function remotely, and even automatically, such as with a computer.
Circuit breakers typically provide status feedback by a visual indication only (e.g., by the position of the circuit breaker handle, by an indication window).
Some circuit breakers employ a status contact for reporting the status of the circuit breaker""s separable contacts. For example, electrical switching devices may optionally include an auxiliary connection or an auxiliary switch located therein to externally indicate the status of the device. Such an auxiliary connection may include, for example, a connection from an internal auxiliary switch to a bell alarm and/or other external circuits for enunciating and/or monitoring the open/closed/tripped status of the electrical switching device.
U.S. Pat. Nos. 5,301,083 and 5,373,411 describe a remotely operated circuit breaker, which introduces a second pair of switching relay contacts in series with the main separable contacts. The main contacts still interrupt the overcurrent, while the secondary contacts perform the discretionary switching operations (e.g., load shedding). The secondary contacts are controlled by a solenoid, which is spring biased to close the contacts. Feedback circuitry, including normally open and normally closed auxiliary feedback contacts, provides a status indication of the condition of the secondary contacts.
Known circuit breakers of such types only provide the status of the switching contacts. There is a need, therefore, to also provide the status of the main contacts.
A panelboard holds a plurality of electrical switching devices, each of which is connected between one or more power sources and a separate load. An example of an external computer for a panelboard is disclosed in U.S. Pat. No. 4,918,566. It is also known to employ a computer within a panelboard.
It is known to employ electronic control, such as a computer, for controlling the solenoids of a plurality of circuit breakers in a panelboard. It is also known to employ the computer to monitor the status of the circuit breakers in a panelboard from the status contacts.
Typically, there are significant space limitations in relatively small circuit breakers. Normally, there is insufficient room for an extra status-reporting wire on the circuit breaker housing due to the significant thickness of UL-approved insulated wire that is required for external wiring. Furthermore, in view of the typical count of circuit breakers in a panelboard, it is undesirable to carry an extra status-reporting wire for each circuit breaker in the panelboard.
There is a need, therefore, for an improved circuit breaker that reports the status of both the main and relay switching contacts.
There is a further need for such a remotely controllable circuit breaker which is simple and economical.
There is a still further need for an improved electrical distribution panel that monitors the status of both main and relay switching contacts of its circuit breakers.
These needs and others are satisfied by the invention, which is directed to a circuit breaker, which includes an input terminal electrically connected to main and secondary auxiliary switches; an output terminal; a first circuit element electrically connected between the main auxiliary switch and the output terminal; and a second circuit element electrically connected between the secondary auxiliary switch and the output terminal. In this manner, the user is able to distinguish between a remote operation that opens or closes the secondary contacts from the opening or closing of the main contacts. Furthermore, this permits four different remote statuses to be communicated to an electrical distribution panel, such as a panelboard, by using a conventional input voltage in combination with a single sensing lead for each circuit breaker in the panelboard.
As one aspect of the invention, a circuit breaker comprises: a first set of separable contacts; a first operating mechanism for operating the first set of separable contacts; a second set of separable contacts in series with the first set of separable contacts; a second operating mechanism for operating the second set of separable contacts; a first auxiliary switch responsive to the first operating mechanism; a second auxiliary switch responsive to the second operating mechanism, the second auxiliary switch electrically connected to the first auxiliary switch; a first terminal electrically connected to the first and second auxiliary switches; a second terminal; a first circuit element electrically connected between the first auxiliary switch and the second terminal; and a second circuit element electrically connected between the second auxiliary switch and the second terminal.
The first circuit element may be a first resistance element, and the second circuit element may be a different second resistance element. Preferably, the first resistance element has a first resistance, and the second resistance element has a second resistance which is about two times the first resistance.
The first circuit element may be a first diode having a first polarity; and the second circuit element may be a second diode having a different second polarity. Preferably, the first diode has a cathode electrically connected to the second terminal; and the second diode has an anode electrically connected to the second terminal.
As another aspect of the invention, an electrical distribution panel comprises: a circuit breaker comprising: a first set of separable contacts having an open state and a closed state, a first auxiliary switch responsive to the open and closed states of the first set of separable contacts, a second set of separable contacts in series with the first set of separable contacts, the second set of separable contacts having an open state and a closed state, a second auxiliary switch responsive to the open and closed states of the second set of separable contacts, the second auxiliary switch electrically connected to the first auxiliary switch, an input terminal electrically connected to both of the first and second auxiliary switches, an output terminal, a first circuit element electrically connected between the first auxiliary switch and the output terminal, and a second circuit element electrically connected between the second auxiliary switch and the output terminal; an enclosure housing the circuit breaker; a power source energizing the input terminal of the circuit breaker, the power source having a common reference; a bridge rectifier electrically connected between the output terminal and the common reference of the power source, the bridge rectifier having an output; and means for determining one of four states from the output of the bridge rectifier based upon four corresponding states of the first and second auxiliary switches of the circuit breaker and the open and closed states of the first and second sets of separable contacts.
As a further aspect of the invention, an electrical distribution panel comprises: a plurality of circuit breakers each of which comprises: a first set of separable contacts having an open state and a closed state, a first auxiliary switch having two states responsive to the open and closed states of the first set of separable contacts, a second set of separable contacts in series with the first set of separable contacts, the second set of separable contacts having an open state and a closed state, a second auxiliary switch having two states responsive to the open and closed states of the second set of separable contacts, the second auxiliary switch electrically connected to the first auxiliary switch, an input terminal electrically connected to both of the first and second auxiliary switches, an output terminal, a first circuit-element electrically connected between the first auxiliary switch and the output terminal, and a second circuit element electrically connected between the second auxiliary switch and the output terminal; an enclosure housing the circuit breakers; a power source energizing the input terminal of the circuit breakers, the power source having a common reference; and means for determining one of four states from the output terminal of each of the circuit breakers based upon the two states of the first auxiliary switches and the two states of the second auxiliary switches of each of the circuit breakers.
As another aspect of the invention, an electrical distribution panel comprises: an N-pole circuit breaker comprising: N sets of first separable contacts, each of the first separable contacts having an open state and a closed state, a first auxiliary switch responsive to the open and closed states of one of the N sets of first separable contacts, N sets of second separable contacts each of which is in series with a corresponding one of the first separable contacts, each of the second separable contacts having an open state and a closed state, N second auxiliary switches each of which is responsive to the open and closed states of a corresponding one of the second separable contacts, an input terminal electrically connected to the first auxiliary switch and the second auxiliary switches, an output terminal, a first circuit element electrically connected between the first auxiliary switch and the output terminal, and N second circuit elements each of which is electrically connected between a corresponding one of the second auxiliary switches and the output terminal; an enclosure housing the circuit breaker; a power source energizing the input terminal of the circuit breaker, the power source having a common reference; and means for determining greater than N states from the output terminal based upon 2N states of the first and second auxiliary switches of the circuit breaker.
A principal object of the invention is to provide state information for two or more different sets of separable contacts, each having an open state and a closed state, on a single output terminal.